Flash lamp



Aug. 3, 1943.

J. H. DE BOER FLASH LAMP Filed Feb. 15, 1943 IN V EN TOR.

ATTORNEY Patented Aug. 3, 1943 FLASH LAMP Jan Hendrik de Boer, London,England, assignor to The Hartford National Bank and Trust Company,Hartford, Coma, as trustee Application February 15, 1943, Serial No.475,952 In Great Britain May 15, 1941 7 Claims.

My invention relates to flash lamps having an envelope of transparentorganic material, such as acetyl-cellulose.

The word "transparent as used herein and in the claims is to beunderstood to mean that the material transmits those light rays whichare used for photographic purposes.

Although flash lamps having envelopes of the above type have severaladvantages from the production view point, I have found that they haveseveral disadvantages which seriously effect their commercialusefulness. Probably the most serious disadvantage is that there isdiffusion of gases through the envelope of organic material and thisdeleteriously efl'ects the proper functioning of the lamps. Moreparticularly, if the lamp is filled with oxygen at a pressure below at-'mospheric pressure, for instance 42 cm. to 57 cm. Hg, air will graduallydiffus into the lamp and form a mixture of oxygen and nitrogen atatmospheric pressure. At first the nitrogen will form a small amount ofthe mixture, but after some time, due to further diflusion, the mixturewithin the lamp will approach 20% oxygen and 80% nitrogen.

The above difllculties are very seriou because to secure the desiredactinic characteristics it is essential that the filling of a flash lampcomprise only certain gases and that these gases be present inpredetermined quantities and at a predetermined pressure. Usually thefilling comprises only oxygen at a predetermined pressure, but in somecases other gases such as oxygen-producing gases and insert gases, areadded.

In accordance with the invention I overcome the above difllcultiesby-providing the envelope with a sealing layer of regenerated cellulose.This layer may be formed as an intermediate sandwiched between twolayers of transparent organic material, or may be a layer on the innerwall of an envelope consisting of organic material. I prefer to form theenvelope of a cellulose derivative which can be partially converted backI into cellulose because this makes it possible to form the layer ofregenerated cellulose from a Fisure 1 is a sectionized side-view or aflash lamp embodying my invention,

Fig. 2 is a sectionized side-view of a flash lamp according to anotherembodiment of the invention, and

Fig. 3 is a sectionized view on an enlarged scale of a portion or thelamp shown in Figure 2.

The flash lamp shown in Figure 1 comprises an envelope having acup-shaped upper portion I and a plate-shaped bottom portion 2. Portionl is formed of an outer layer-3, an inner layer I and an intermediatelayer 4. Layers 3 and I are formed or a transparent organic material,such as a non-inflammable cellulose material which exhibits someelasticity and preferably some flexibility. Suitable materials for thispurpose are cellulose acetate, polyvinyl chloride, urea formaldehyderesin, polyacrylic acid or ethers, polyvinyl ethers. V

In accordance with the invention the intermediate layer 4 is formed ofregenerated cellulose which has been produced by converting a cellulosederivative into cellulose again. Such a layer is highly resistant todiffusion of gases.

The intermediate layer 4 of regenerated cellulose may be formed byapplying regenerated cellulose to the layer 5 and then forming the layer3 thereon. However, Ipreier to form layer- 4 from a surface portion ofeither layer 3 or '6. In this case I form layer 3 or 6 of a cellulosederivative which can be partially converted back into cellulose. Forinstance layer 5 may be of acetylcellulose and a surface portionsaponified to form layer 4 of regeneratedcellulose. This saponifl-=cation may be performed by a solution of caustic soda or potassiumhydroxide preferably in methylor ethylalcoholic solution.

The bottom portion 2 comprises a layer 8 of an organic material, anintermediate layer 1 of regenerated cellulose and a layer 8 of anorganic material. The materials of layers 8 and 8 may be the same as thematerials oi layers 3 and 5, whereas the material of layer 1 may be thesame as that of layer 4 and may be formed in a similar manner.

The lower end or portion I is provided with an annular flange 9 by whichit is sealed to the bottom portion 2. It will be noted that the layers Iand 8 do not extend into the flange andthat the seal at the flange isformed between the layers 4 and l of regenerated cellulose. This makesit possible to obtain a tight Joint.

Sealed into the portion 2 are two lead-in wires it which, at their upperends, support suitable ignition means H, such as a filament providedwith a small amount or zirconium, aluminium or phosphorus powder.

The container is provided with a quantity of combustible material 62,shown as a thin wire of aluminium or aluminium-magnesium alloy. Insteadof wire,,the usual foils may be used. The lamp also contains a fillingof a combustion supporting gas such as oxygen. Due to the use of thesealing layers l and l of regenerated cellulose,.the gas may be at arelatively high pressure, for instance about atmospheres, without dangeroi diiTusion, and because of this a very intense flash is obtained andthe lamp can be of small size.

I may also place in the lamp solid substances which under the conditionsof reaction within the envelope yield oxygen to supplement the gaseousfilling. According to the speed at which the oxygen is released, thesesolid substances may be associated with the primer or with the metalfoil, wire or powder. In this way a greater quantity of oxygen is madeavailable for the reaction without a corresponding increase in themaximum pressure generated within the envelope. Certain metallic oxidessuch as mercuric oxide, silver oxide and cadmium oxide are suitable.Other examples of suitable substances are so called higher oxides orperoxides such as lead-peroxide, red lead, manganese dioxide, bariumperoxide, silver peroxide, etc. and salts which are capable of releasingoxygen at rather low temperatures, such as alkali-chlorates,perchlorates, permanganates, bichromates, 'chromates, perborates. Evenorganic peroxides, such as benzoylperoxide may be used. In the case ofmercuric oxide, the mercury vapour released within the envelope duringthe reaction may asaaeer bustible material within said container, 2.comaugment the actinic value of the light emitted. I

The flash lamp shown in Figure 2 is similar to that shown in Figure 1and has similarparts indicated by the same reference numerals. However,in the lamp of Figure 2 the inner layers 5 and 8 are omitted. The layers3. and 5 are preferably made of a cellulose derivative which canbeconverted back into cellulose and the layers 4 and l are formed bysaponifying a surface portion of layers 3 and 6.

Figure 3 shows a part of the portion 2 of Fig. 2. However, in Fig. 3 alayer of regenerated cellulose extends along the portion of wires in soas to form a seal between these wires and the layer 6.

Although I have described my invention with reference to specificexamples and constnuctions, I do not desire to be limited thereto,because obvious medifications will readily present themselves to'oneskilled in this'art.

Iclaim:

1. A flash lamp comprising a container, combustible material within saidcontainer, a. combustion-supporting gas within said container,

and means for igniting said material, said container comprising a layerof a transparent orbustion-supporting gas within said container, andmeans for igniting said material, said container comprising two layersof a transparent organic material, and a sealing layer of regeneratedcellulose interposed between said first two layers.

3. A flash lamp comprising a container, combustible material within saidcontainer, a combustion-supporting gas within said container, and meansfor igniting said material, said container comprising a layer of atransparent organic material capable of being converted into celluloseand a sealing layer of regenerated cellulose formed from a surfaceportion of said first layer and covering said first layer.

4. A flash lamp comprising a container hB.V ing two parts, combustiblematerial within said container, a combustion-supporting gas within saidcontainer, and means for igniting said material, each part of saidcontainer comprising a layer of a transparent organic material and asealing layer oi regenerated cellulose, said parts being joined togetherby the layers of regenermaterial, each of said parts comprising a layerof transparent organic material, a sealing layer of regeneratedcellulose covering the inner surface of said cup-shaped part and theflange thereof and a sealing layer'of regenerated cellulose covering thesurface of said plate-shaped part, said parts being sealed together atsaid flange by the layers of regenerated cellulose.

-6. A flash lamp comprising a container, combustible material withinsaid container, a combustion-supporting gas within said container, andmeans for igniting said material including lead-in wires extendingthrough a portion of the container, said portion comprising a layer of atransparent organic material and a sealing layer of regeneratedcellulose, said latter layer surrounding the part of the lead-in wiresextending through the container.

,7. A flash lamp comprising a container, combustible material withinsaid container, a combustion-supporting gas within said container, andmeans for igniting said material, said container comprising an outerlayer of a transparent organic material capable of being converted intoJAN HENDRIK DE BOER.

